CN114778984B - Transformer substation stray current detection method based on earth surface potential change - Google Patents
Transformer substation stray current detection method based on earth surface potential change Download PDFInfo
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Abstract
The invention relates to a detection method for whether stray current in a power system invades an urban transformer substation, and discloses a transformer substation stray current detection method based on earth surface potential change, wherein reference electrodes are arranged near an earth surface network outgoing line in the transformer substation and outside the transformer substation, and earth surface potential signals U are synchronously acquired by using an earth surface potential sensor 1 (t) and U 2 (t). Calculate the current time t and U in the first 10 seconds 1 (t) and U 2 Average value k of (t) 1 (t)、k 2 (t). Calculating Δh=k 2 (t)‑k 1 (t) if 5 Δh in succession satisfy Δh>And 0.2, judging that stray current invades the transformer substation at the current moment.
Description
Technical Field
The invention relates to a detection method for judging whether stray current invades an urban transformer substation in a power system, in particular to a method for judging whether the transformer substation is invaded by the stray current by utilizing the change of ground surface potential.
Background
The subway power supply system of China mainly adopts DC1500V, and mainly utilizes the steel rail to carry out backflow, and because the steel rail has longitudinal resistance, the steel rail cannot completely insulate the ground, and part of the steel rail is pulled to backflow and leak into the soil so as to form stray current. When stray current flows into the transformer substation grounding net, natural corrosion potential forward shift of the grounding net can be caused, and corrosion of the grounding net is accelerated. Faults such as corrosion, breakage and the like of the grounding grid are found in time, and the method has important significance for guaranteeing safe operation of the grounding grid. When considering the corrosion caused by stray current to the grounding grid, the most intuitive is to monitor the magnitude and flow direction of the stray current in the grounding grid and the nearby soil, but the existing means cannot be directly monitored. When the current flows out between the soil and the metal, a pressure drop is generated in the soil and a certain surface potential is formed. The earth surface potential can indirectly reflect the actual condition of the underground conductor, and is used as one of indexes for measuring the safety of the grounding network, and reflects the overall grounding safety of the transformer substation. Therefore, the change condition of the earth surface potential is necessary to be studied to judge the invasion condition of the stray current, and the method can provide guidance for the problem of corrosion of the grounding network caused by the stray current.
In engineering application, the surface potential change is used for judging that the stray current interference is mainly applied to the buried long-circuit pipeline, and the interference condition of the stray current to the pipeline is judged through the surface potential gradient value or the metal natural corrosion potential forward-moving value above the pipeline. The pipeline structure is simple, and pipelines are not distributed in a staggered manner under many conditions, so that the two testing methods can be carried out at any time without long-time monitoring, and the measured data can be compared with the standard value to judge whether the pipeline is interfered by stray current. The generation of direct-current subway stray current is influenced by actual operation parameters of a subway train, so that the leakage position, the size and the like of the stray current have uncertainty, equipment in a transformer substation is numerous and various in operation modes, and the change of the ground surface potential can be time-varying due to the size, the burial depth, the soil resistivity, the distance between the transformer substation and a line and the like of the grounding grid. Therefore, the method for judging the interference of the stray current on the pipeline cannot be directly transplanted to the judgment of the invasion of the stray current on the subway on the transformer substation.
Disclosure of Invention
In order to solve the technical problems in the prior art, the invention provides a method for detecting stray current of a transformer substation based on earth surface potential change, which is to collect earth surface potential signals for a long time by using an earth surface potential sensor, and judge whether the stray current invades the transformer substation or not through the difference value between the earth surface potential signals;
the technical scheme adopted by the invention is as follows:
the method for detecting the stray current of the transformer substation based on the earth surface potential change comprises the following steps:
step 1: embedding a reference electrode Z1 at a point P of a soil area near an outgoing line O point of a grounding grid in a transformer substation, wherein the distance between the O point and the P point is not more than 5 meters; a reference electrode Z2 is embedded at a Q point outside the transformer substation, the Q point is arranged on an extension line of a straight line connected with the O point and the P point, and the distance between the Q point and the transformer substation is not less than 5 meters;
step 2: the earth potential signals U between the O point and the P point and between the O point and the Q point are synchronously collected by using the earth potential sensors M1 and M2 respectively 1 (t) and U 2 (t)；
Step 3: calculating the earth potential signal U within 10 seconds before the current moment 1 Average value k of (t) 1 (t) calculating the surface potential signal U10 seconds before the current time 2 Average value k of (t) 2 (t)；
Step 4: Δh is calculated using the following formula:
Δh＝k 2 (t)-k 1 (t)；
if the continuous 5 delta h satisfy delta h >0.2, judging that stray current invades the transformer substation at the current moment.
The invention introduces a scientific technical means for judging whether stray current invades the transformer substation: the invention utilizes the earth potential sensor to monitor earth potential signals for a long time to judge the condition that the subway stray current invades the transformer substation. Traditional methods for judging the interference of the stray current on the pipeline are mostly used for single-point short-time test, test data are easily affected by test staff and test positions, and stability of test results cannot be guaranteed. According to the invention, from actual, according to the plurality of devices in the transformer substation, the subway train receiving and transmitting and running intervals have certain regularity, and whether stray current invades the transformer substation can be judged at any moment by utilizing the difference value between the ground potential signals.
Preferably, the signal sampling frequency of the earth surface potential sensors M1 and M2 in the step 2 is more than or equal to 1Hz, and the synchronization error is less than or equal to 1 mu s; the measuring ranges of the earth surface potential sensors M1 and M2 are less than or equal to + -5V, and the precision values are less than or equal to 0.1%; the anodes of the earth surface potential sensors M1 and M2 are respectively connected with a grounding grid outgoing line of an O point, and the cathodes of the earth surface potential sensors are respectively connected with a reference electrode Z1 and a reference electrode Z2.
Preferably, the reference electrode Z1 and the reference electrode Z2 are copper sulfate reference electrodes.
The beneficial effects of the invention include:
1. the invention introduces a scientific technical means for judging whether stray current invades the transformer substation: the invention utilizes the earth potential sensor to monitor earth potential signals for a long time to judge the condition that the subway stray current invades the transformer substation. Traditional methods for judging the interference of the stray current on the pipeline are mostly used for single-point short-time test, test data are easily affected by test staff and test positions, and stability of test results cannot be guaranteed. According to the invention, from actual, according to the plurality of devices in the transformer substation, the subway train receiving and transmitting and running intervals have certain regularity, and whether stray current invades the transformer substation can be judged at any moment by utilizing the difference value between the ground potential signals.
2. The adoption of the copper sulfate reference electrode with better stability and the surface potential sensor with higher precision and smaller measuring range can effectively eliminate measurement errors caused by data instability, avoid error of test results and have stronger anti-interference capability.
Drawings
FIG. 1 is a flow chart of the method of the present invention;
FIG. 2 is a schematic diagram of the overall arrangement of the test apparatus of the present invention;
FIG. 3 is a schematic view of the equipment arrangement of the present invention in carrying out experiments;
FIG. 4 is a schematic diagram showing the detection results of the experiment conducted by the present invention.
Detailed Description
For the purposes of making the objects, technical solutions and advantages of the embodiments of the present application more clear, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application, and it is apparent that the described embodiments are only some embodiments of the present application, but not all embodiments. The components of the embodiments of the present application, which are generally described and illustrated in the figures herein, may be arranged and designed in a wide variety of different configurations. Thus, the following detailed description of the embodiments of the present application, as provided in the accompanying drawings, is not intended to limit the scope of the application, as claimed, but is merely representative of selected embodiments of the application. All other embodiments, which can be made by those skilled in the art based on the embodiments of the present application without making any inventive effort, are intended to be within the scope of the present application.
The invention is described in further detail below with reference to fig. 1 and 4:
referring to fig. 1 and 2, the method for detecting the stray current of the transformer substation based on the earth surface potential change comprises the following steps:
step 1: embedding a reference electrode Z1 at a point P of a soil area near an outgoing line O point of a grounding grid in a transformer substation, wherein the distance between the O point and the P point is not more than 5 meters; a reference electrode Z2 is embedded at a Q point outside the transformer substation, the Q point is arranged on an extension line of a straight line connected with the O point and the P point, and the distance between the Q point and the transformer substation is not less than 5 meters;
step 2: the earth potential signals U between the O point and the P point and between the O point and the Q point are synchronously collected by using the earth potential sensors M1 and M2 respectively 1 (t) and U 2 (t)；
Step 3: calculating the earth potential signal U within 10 seconds before the current moment 1 Average value k of (t) 1 (t) calculating the surface potential signal U10 seconds before the current time 2 Average value k of (t) 2 (t)；
Step 4: Δh is calculated using the following formula:
Δh＝k 2 (t)-k 1 (t)；
if the continuous 5 delta h satisfy delta h >0.2, judging that stray current invades the transformer substation at the current moment.
The invention introduces a scientific technical means for judging whether stray current invades the transformer substation: the invention utilizes the earth potential sensor to monitor earth potential signals for a long time to judge the condition that the subway stray current invades the transformer substation. Traditional methods for judging the interference of the stray current on the pipeline are mostly used for single-point short-time test, test data are easily affected by test staff and test positions, and stability of test results cannot be guaranteed. According to the invention, from actual, according to the plurality of devices in the transformer substation, the subway train receiving and transmitting and running intervals have certain regularity, and whether stray current invades the transformer substation can be judged at any moment by utilizing the difference value between the ground potential signals.
In the step 2, the signal sampling frequencies of the earth surface potential sensors M1 and M2 are all more than or equal to 1Hz, and the synchronization error is less than or equal to 1 mu s; the measuring ranges of the earth surface potential sensors M1 and M2 are less than or equal to + -5V, and the precision values are less than or equal to 0.1%; the anodes of the earth surface potential sensors M1 and M2 are respectively connected with a grounding grid outgoing line of an O point, and the cathodes of the earth surface potential sensors are respectively connected with a reference electrode Z1 and a reference electrode Z2.
The reference electrode Z1 and the reference electrode Z2 adopt copper sulfate reference electrodes.
Experiment was conducted
In order to make the content of the invention clearer and more visual, the method and the device provided by the invention are used for detecting the stray current for a certain simple grounding grid. As shown in fig. 3, the simple grounding grid is formed by welding galvanized round steel with the diameter of 8mm, the overall size of the grounding grid is 2m x 2m, the grid size is 0.5m x 0.5m, the lengths of five vertical grounding poles are all 0.8m, and the burial depth of the grounding grid is 0.2m. The sampling frequency of the test signal is 1Hz, the measuring range of the surface potential sensor is + -2V, the precision value is 0.1%, and the synchronization error is not more than 1 mu s. In the test, the outgoing line of the grounding network in the transformer substation is represented by a vertical grounding electrode. One of the vertical grounding electrodes is selected as an O point, and the reference electrodes Z1 and Z2 are respectively buried at two points P, Q. The anodes of the earth surface potential sensors M1 and M2 are respectively connected with a grounding grid outgoing line of an O point, and the cathodes of the M1 and M2 are respectively connected with Z1 and Z2. And injecting 0.073A direct current into the other vertical grounding electrode by using a constant current source, and simulating stray current to invade the transformer substation. As can be seen from the detection result, when there is a stray current invasion, the earth potential signals U are collected by M1 and M2 within any 10 seconds 1 (t) and U 2 Average value k of (t) 1 (t)、k 2 (t) differ by about 1.5, where k 2 (t)-k 1 (t) ≡1.5. I.e. to satisfy 5 Δh in succession>0.2. It is thus possible to detect whether stray currents invade the substation based on changes in the earth's surface potential.
The foregoing examples merely represent specific embodiments of the present application, which are described in more detail and are not to be construed as limiting the scope of the present application. It should be noted that, for those skilled in the art, several variations and modifications can be made without departing from the technical solution of the present application, which fall within the protection scope of the present application.
Claims (3)
1. The method for detecting the stray current of the transformer substation based on the earth surface potential change is characterized by comprising the following steps of:
step 1: embedding a reference electrode Z1 at a point P of a soil area near an outgoing line O point of a grounding grid in a transformer substation, wherein the distance between the O point and the P point is not more than 5 meters; a reference electrode Z2 is embedded at a Q point outside the transformer substation, the Q point is arranged on an extension line of a straight line connected with the O point and the P point, and the distance between the Q point and the transformer substation is not less than 5 meters;
step 2: the earth potential signals U between the O point and the P point and between the O point and the Q point are synchronously collected by using the earth potential sensors M1 and M2 respectively 1 (t) and U 2 (t)；
Step 3: calculating the earth potential signal U within 10 seconds before the current moment 1 Average value k of (t) 1 (t) calculating the surface potential signal U10 seconds before the current time 2 Average value k of (t) 2 (t)；
Step 4: Δh is calculated using the following formula:
Δh＝k 2 (t)-k 1 (t)；
if the continuous 5 delta h satisfy delta h >0.2, judging that stray current invades the transformer substation at the current moment.
2. The method for detecting the stray current of the transformer substation based on the earth surface potential change according to claim 1, wherein the signal sampling frequency of the earth surface potential sensors M1 and M2 in the step 2 is more than or equal to 1Hz, and the synchronization error is less than or equal to 1 mu s; the measuring ranges of the earth surface potential sensors M1 and M2 are less than or equal to + -5V, and the precision values are less than or equal to 0.1%; the anodes of the earth surface potential sensors M1 and M2 are respectively connected with a grounding grid outgoing line of an O point, and the cathodes of the earth surface potential sensors are respectively connected with a reference electrode Z1 and a reference electrode Z2.
3. The method for detecting stray current of a transformer substation based on surface potential change according to claim 1, wherein the reference electrode Z1 and the reference electrode Z2 are copper sulfate reference electrodes.
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